I have an insane crush on a co-worker, and she knows, but the signals are mixed.. what do i do?

It seemed like it was going well at first, and then it didn't, this went on for a while, and then she did the whole, "we work together" thing, so I gave up, and then it seemed like I screwed up, and I've been in a ridiculous amount sorrow and pain for over a month. There is nothing more that I want in this world than a chance with her. I can't even look at her anymore because it hurts. So should I just go all out and say that I really want a chance, because I can't sleep, eat, have fun or be happy. I've been with others, but never have I wanted someone so much... to make matters worse, I try forgetting about her and all I do is dream about her. I'm not an emotional person, but she has messed me up... I honestly can't do anything without thinking about her.